The present invention relates to a method for cutting materials using a laser beam, which emerges from a cutting head comprising a cutting nozzle with an inner edge and is absorbed on the cutting front, the axis of the laser beam being moved along a cutting line with a fixed orientation in the cutting direction of a workpiece relative to said workpiece.
The cutting of a workpiece with a laser beam is an established cutting method. It assumes a leading function among the laser-supported manufacturing methods in industrial applications. One demand continuously made by the users is enhanced efficiency of the method while the quality requirements are increasing.
Essential features that must be guaranteed in fusion cutting, which includes laser beam cutting, are efficiency of the process, quality of the cut edge, ripple amplitude as small as possible, no formation of adherent drosses and no oxidation.
Likewise, shorter processing times and the high-quality cutting of large sheet thicknesses are trends in today's industrial development. Ever increasing laser performances and systems with high-quality drives are introduced into the manufacturing process.
The known techniques for cutting metals with laser radiation are subdivided, by the mechanisms involved in the input of the cutting energy, into                laser beam cutting with reactive cutting gas jet, and        laser beam cutting with inert cutting gas jet.        
In laser beam cutting with a reactive cutting gas jet (e.g. oxygen, compressed air), the laser beam and an exothermic chemical reaction jointly provide the cutting power. Techniques for laser beam cutting with a reactive cutting gas jet are further distinguished by features as to whether the laser beam dominantly acts in the cut kerf (laser beam reactive gas cutting) or is additionally irradiated onto the upper side of the sheet (burning stabilized laser beam flame cutting).
In the case of laser beam cutting with an inert cutting gas jet (e.g. nitrogen), the laser beam provides the cutting power. Laser beam cutting with an inert cutting gas jet is further distinguished by the different mechanisms for accelerating/ejecting the melt. In addition to the cutting gas jet, the molten material may evaporate and evaporation may accelerate fusion. With an increasing advance speed the driving action is increasing due to evaporation. A distinction is made between three variants:                Laser beam fusion cutting:        
The temperature on the surface of the melt remains below the evaporation temperature and the melt is only ejected by the cutting gas jet. This variant of the method is employed in industry with thin, medium-sized and thick sheets. The melt flows out dominantly at the apex of the cutting front, in front of the laser beam axis. The formation of adherent drosses as is observed at cutting speeds that are too high or too low impairs the quality.                Fast cutting:        
The evaporation temperature is exceeded on the lower part of the cutting front, and the ejecting action due to the cutting gas and that due to the evaporating material are comparable. The melt flows out dominantly in the front portion of the cutting front, at the right and left side next to the laser beam axis. This variant can be employed in the case of thin and medium-sized sheets. The whisker formation observed at an excessively high cutting speed is detrimental to the quality.                High-speed cutting:        
The evaporation temperature is exceeded almost over the whole cutting front. The driving action due to evaporation is dominant. The melt flows around the laser beam axis and occludes part of the cut kerf following the laser beam and is there ejected by the action of the cutting gas. This variant of the method is used for thin sheets.
The prior art regarding the cutting of metals with laser radiation describes measures for optimizing the process with constantly set parameters of the laser cutting machine. Such measures aim at:                exploiting the laser beam power as fully as possible (illumination of the cutting front) and decreasing the power losses caused by heating of material adjoining the cut kerf, and        increasing the cutting gas efficiency to eject the melt as completely as possible.        
The literature describes that the power of the laser beam is partly absorbed by the material and partly reflected. The absorbed portion is available for the cutting process and is divided into effective power and various power losses.
It is also known from the literature that in the cutting of narrow contours the cutting speed should be reduced because the acceleration of the cutting machine is limited. To avoid an undesired broadening of the cut kerf due to excessive laser power and the formation of adhering drosses or whiskers due to an excessively low cutting speed, the laser power can be modulated.